Contemplating out loud, for the past couple of weeks gravity has been stuck in my mind, when one thinks of a world with no gravity one may tend to think of space, science is a continues work in progress were one individual improves upon the others works, generally speaking

"Newton's Principia formulated the laws of motion and universal gravitation, which dominated scientists' view of the physical universe for the next three centuries. By deriving Kepler's laws of planetary motion from his mathematical description of gravity, and then using the same principles to account for the trajectories of comets..."

http://en.wikipedia.org/wiki/Isaac_Newton

The point that I am trying to get at is that, before understanding had progressed to the level of Newton, they must have been a time where people were either ignorant of gravity or they might have thought of it as something else
(they weren't flying of every where as would happen in space), the absense of an understanding of gravity highlights the knowledge capabilities (used or unused) of the primitive man in the sense that in space they is no gravity, and that the clearer the past the more we can understand our future.

To conclude gravitation is understood by all who are on earth (what goes up must come down), to even ask about it, you would get odd stares, its become part of what one would call common sense, but what startles me the most is that even with this knowledge or common sense as some might put it, we hold are view with such arrogance that it clouds such understanding that all our knowledge springs from the same river.